The present invention relates generally to methods and apparatus of semiconductor manufacturing process. More particularly, the invention provides methods and apparatus for excimer curing.
Materials such as silicon oxide (SiOx), silicon carbide (SiC) and carbon doped silicon oxide (SiOCx) films find widespread use in the fabrication of semiconductor devices. One approach for forming such silicon-containing films on a semiconductor substrate is through the process of chemical vapor deposition (CVD) within a chamber. For example, chemical reaction between a silicon supplying source and an oxygen supplying source may result in deposition of solid phase silicon oxide on top of a semiconductor substrate positioned within a CVD chamber. As another example, silicon carbide and carbon-doped silicon oxide films may be formed from a CVD reaction that includes an organosilane source including at least one Si—C bond.
Water is often a by-product of the CVD reaction of organosilicon compounds. As such, water can be physically absorbed into the films as moisture or incorporated into the deposited film as Si—OH chemical bond. Either of these forms of water incorporation are generally undesirable. Accordingly, undesirable chemical bonds and compounds such as water are preferably removed from a deposited carbon-containing film. Also, in some particular CVD processes, thermally unstable organic fragments of sacrificial materials need to be removed.
One conventional method used to address such issues is a thermal anneal. The energy from such an anneal replaces unstable, undesirable chemical bonds with more stable bonds characteristic of an ordered film thereby increasing the density of the film. Conventional thermal anneal steps are generally of relatively long duration (e.g., often between 30 min to 2 hrs) and thus consume significant processing time and slow down the overall fabrication process.
Another technique to address these issues utilizes ultraviolet radiation to aid in the post treatment of CVD silicon oxide, silicon carbide and carbon-doped silicon oxide films. The use of UV radiation for curing and densifying CVD films can reduce the overall thermal budget of an individual wafer and speed up the fabrication process. A number of various UV curing systems have been developed which can be used to cure films deposited on substrates.
Usually, an UV curing system has either mercury vapor lamps or metal halide doped mercury lamps powered by microwave generator. UV lamps generate light across a broad band of wavelengths from 170 nm to 600 nm. However, UV lamps usually have a short lifetime and provide low output of radiation at wavelength less than about 400 nm. Furthermore, particularly at wavelength less than 250 nm, the power output of UV lamps declines with the increasing use of the UV lamps.
Accordingly, improvements to existing UV curing systems and methods are desirable.